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Temperature Adjustment of UK Energy Statistics
Iain MacLeay
Temperature adjustment of UK Energy Statistics Iain MacLeay – May 2011
Between 2009 and 2010 what happened to UK energy consumption ?
Did it
a. Rise by 3.9%
b. Rise by 2.9%
c. Remain broadly unchanged
d. Fall by 0.6%
Temperature adjustment of UK Energy Statistics Iain MacLeay – May 2011
Annual average temperature (degrees Celsius)
8.0
8.5
9.0
9.5
10.0
10.5
11.0
2000 2002 2004 2006 2008 2010
Deg
rees
cels
ius
Temperature adjustment of UK Energy Statistics Iain MacLeay – May 2011
•
-6
-4
-2
0
2
4
-30,000 -20,000 -10,000 0 10,000 20,000
Tem
pera
ture
chan
ge
GWh change
Change in gas supply v temperature change
Temperature adjustment of UK Energy Statistics Iain MacLeay – May 2011
Primary Energy Consumption
Million tonnes of oil equivalent
UnadjustedSeasonally and temperature adjusted (annual rates)
2009 211.1 212.6
2010 217.3 211.3
Per cent change +2.9 -0.6
Temperature adjustment of UK Energy Statistics Iain MacLeay – May 2011
Statistical Model
Y = C * I * S * TD * E * tempWhere:Y = observed time seriesC = trend-cycleI = irregular componentS = seasonal factorTD = trading day effectE = Easter effecttemp = Temperature coefficient
Note: Model can be arithmetic rather than multiplicative Y = C + I + S + TD + E + temp; or a combination of the two.
Temperature adjustment of UK Energy Statistics Iain MacLeay – May 2011
Temperature correction
Y / temp = C * I *S * TD * E
Assume no temperature, Easter or trading day effects then:
Y = C * I * S
And the seasonally and temperature adjusted series is
Y / S = C * I
Temperature adjustment of UK Energy Statistics Iain MacLeay – May 2011
Two main statistical techniques used• Regression
– Easter– Trading days– Temperature effects
• Moving averages– Trend-cycle– Seasonal component
+ ARIMA modelling to help improve the calculation of the moving averages (extend time series by forecasting one year of additional data)
Temperature adjustment of UK Energy Statistics Iain MacLeay – May 2011
How do we currently adjust for temperature• Gas
– National Grid provide temperature adjusted series as well as the raw data for gas
– Adjustments are smaller in the summer months of July and August. Largest adjustments in fact appear in Spring and Autumn
– Does this seem sensible ?• Coal
– Adjusted by factor of 2.1. – If temperature is 2 degrees above “normal” then factor = (2 * 2.1)
= 4.2. Raw data is divided by 0.958 resulting in temperature adjustment increasing the series.
– Warm weather – use less energy – so temperature adjusted series should be higher
– Same adjustment used irrespective of season
Temperature adjustment of UK Energy Statistics Iain MacLeay – May 2011
Temperature adjustment
Alternative methods1. Use same factors for each month – or specific
factors for each month2. Use monthly average temperatures (current
practice) or degree days (only use heating if daily temperature above/below threshold)
3. Growth in cooling – should this be adjusted for?Data• DECC receive data from the Met Office (17 stations
reporting daily max and min temperatures)
Temperature adjustment of UK Energy Statistics Iain MacLeay – May 2011
Coal data
Temperature adjustment of UK Energy Statistics Iain MacLeay – May 2011
Coal data
Temperature adjustment of UK Energy Statistics Iain MacLeay – May 2011
Coal data
Temperature adjustment of UK Energy Statistics Iain MacLeay – May 2011
Average monthly temperature
Temperature adjustment of UK Energy Statistics Iain MacLeay – May 2011
Heating degree days
Temperature adjustment of UK Energy Statistics Iain MacLeay – May 2011
Temperature adjustment factors
Temperature adjustment of UK Energy Statistics Iain MacLeay – May 2011
Final factors – using degree day methodology
Temperature adjustment of UK Energy Statistics Iain MacLeay – May 2011
0
2,000
4,000
6,000
8,000
10,000
12,000
14,000
16,000
2008 2009 2010
ktoe
Domestic gas consumption
Raw dataTemperature correctedSeasonally and temperature corrected
Temperature adjustment of UK Energy Statistics Iain MacLeay – May 2011
UK energy growth 2009 to 2010
Raw data Temperature corrected data
Primary energy consumption
+2.9% -0.6%
Final energy consumption
+3.9% +0.1%
Domestic gas consumption
+15.0% -0.4%
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